In recent years, electromagnetic waves in a terahertz frequency band intermediate between radio waves and light (i.e., electromagnetic waves having a frequency of 1012 Hz range and a wavelength ranging about 30 μm to 1 mm, hereinafter referred to as “THz wave”) have been attracting attention as electromagnetic waves that directly reflect information from substances. Techniques relating to bolometer-type infrared light detectors having a thermal isolation structure have been applied to detection of THz waves. Conventional detectors of such a kind include bolometer-type THz wave detectors, which are, for example, disclosed in JP 2008-241438 A and in a technical paper published in SPIE (Oda et al., Proceedings of SPIE, Vol. 6940 (2008) p. 69402Y-1-69402Y-12).
FIG. 8 shows a pixel structure of a conventional two-dimensional bolometer-type THz wave detector. In the bolometer-type THz wave detector 20 shown in FIG. 8, a reflective film 3 that reflects incident THz waves and contacts 4 for connection to a Read-out integrated circuit 2a or the like are formed on a circuit substrate 2 in which the Read-out integrated circuit 2a is formed. A first protecting film 5 is formed on the reflective film 3 and the contacts 4. A supporting portion 13 composed of a second protecting film 6, a third protecting film 8, electrode wiring 9 and a fourth protecting film 10 is formed on the contacts 4. The Read-out integrated circuit 2a and the electrode wiring 9 are connected to each other through the contacts 4. The supporting portion 13 holds a temperature detecting portion (diaphragm) 14 composed of the second protecting, film 6, a bolometer thin film 7, the third protecting film 8, the fourth protecting film 10 and an absorbing film 11 in a hollow space (air gap 15). The electrode wirings 9 are connected to both ends of the bolometer thin film 7.